Device for optically scanning and measuring an environment

ABSTRACT

With a device for optically scanning and measuring an environment which is designed as a laser scanner, with a light emitter, which emits an emission light beam, with a light receiver which receives a reception light beam which is reflected by an object in the surroundings of the laser scanner or scattered otherwise, with a control and evaluation unit which determines the distance to the object for a multitude of measuring points, wherein the emission light beam is a superposition of three laser beams having different wave lengths, which define the three-dimensional color space.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a National Stage Application of PCT Application No. PCT/EP2010/001779 filed on Mar. 22, 2010, which claims the benefit of U.S. Provisional Patent Application No. 61/299,566 filed on Jan. 29, 2010, and of pending German Patent Application No. DE 10 2009 015 920.7, filed on Mar. 25, 2009, and which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The invention relates to a device for optically scanning and measuring an environment.

By means of a device such as is known for example from DE 20 2006 005 643, and which is designed as a laser scanner, the environment of the laser scanner can be optically scanned and measured. For gaining additional information, a line scan camera, which takes RGB signals, is mounted on the laser scanner, so that the measuring points of the scan can be completed by color information. The camera holder is rotatable. To avoid parallax errors, the camera, for taking its records, is swiveled onto the vertical rotational axis of the laser scanner, and the laser scanner is lowered until the camera has reached the horizontal rotational axis. This method requires a high precision of the components.

SUMMARY OF THE INVENTION

Embodiments of the present invention are based on the object of creating an alternative to the device of the type mentioned hereinabove.

The device according to embodiments of the present invention makes it possible to generate a “colored” emission light beam, so that the reception light beam already gets the color information. A linking of the scan, which is formed by the entity of measuring points with colored pictures or with varicolored pictures after the scan has been made, is no longer necessary. Parallax errors are automatically avoided.

All three laser beams are required for gaining color and brightness information. For determining the distances, however, one laser beam is sufficient, which may be modulated. The laser beam which serves to determine the distance may have a higher intensity than the two other laser beams. The two other laser beams may supply further information on the distance, but, for the rest, they supply largely redundant information which can be used for error corrections.

For special applications or operating modes, it is advantageous if only single, monochromatic laser beams are available. For this purpose, the light emitter may be designed in such a way that, independently of each other, i.e. individually, the three laser beams can be switched on and off and their intensity can be controlled and/or the corresponding lasers can be mounted and dismounted.

To protect the eyes of the user and other persons in the surroundings, it may be advantageous to use the blue laser beam with a wavelength of less than 400 nm. The other two laser beams may have an intensity which is lower than the intensity of the blue laser beam, i.e. the blue laser beam is dominating. In a manner, which is not according to the invention, the laser scanner is designed to generate exclusively the blue laser beam with a wave length of less than 400 nm.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail below on the basis of exemplary embodiments illustrated in the drawings, in which

FIG. 1 shows a partial sectional view of the laser scanner; and

FIG. 2 shows a schematic illustration of the laser scanner.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 2, a laser scanner 10 is provided as a device for optically scanning and measuring the environment of the laser scanner 10. The laser scanner 10 has a measuring head 12 and a base 14. The measuring head 12 is mounted on the base 14 as a unit that can be rotated around a vertical axis. The measuring head 12 has a mirror 16, which can be rotated around a horizontal axis. The intersection point of the two rotational axes is designated center C₁₀ of the laser scanner 10.

The measuring head 12 is further provided with a light emitter 17 for emitting an emission light beam 18. The emission light beam 18 is a superposition of three laser beams R, G and B which, with different wavelengths, are within the visible range of approximately 300 to 1000 nm wavelength, such as 790 nm, 555 nm and 375 nm. The wavelengths of the three laser beams R, G and B are selected in such a way that they define the three-dimensional RGB color space, i.e. that they are distributed well over the visible range. The laser emitter 17 has three laser diodes 17R, 17G, 17B (or other lasers), each of which generates one of the three laser beams R, G or B. The superposition can take place by feeding the three free laser beams R, G and B into the collimator of the light emitter 17 or by feeding them into a common optical fiber which is then fed to the collimator.

At least one of the three laser beams R, G, B in the emission light beam 18, and in an embodiment all three laser beams R, G, B, are amplitude-modulated, for example with a sinusoidal or with a rectangular-waveform modulation signal. The emission light beam 18 is emitted by the light emitter 17 onto the mirror 16, where it is deflected and emitted to the environment. A reception light beam 20, which is reflected in the environment by an object O or scattered otherwise, is captured by the mirror 16, deflected and directed onto a light receiver 21. The direction of the emission light beam 18 and of the reception light beam 20 results from the angular positions of the mirror 16 and the measuring head 12, which depend on the positions of their corresponding rotary drives which, in turn, are registered by one encoder each. A control and evaluation unit 22 has a data connection to the light emitter 17 and the light receiver 21 in measuring head 12, whereby parts of such unit can be arranged also outside the measuring head 12, for example a computer connected to the base 14. The control and evaluation unit 22 determines, for a multitude of measuring points X, the distance d between the laser scanner 10 (i.e. the center C₁₀) and the (illuminated point at) object O, from the propagation time of emission light beam 18 and reception light beam 20. For this purpose, the phase shift between the two light beams 18 and 20 is determined and evaluated.

Scanning takes place along a circle by means of the relatively quick rotation of the mirror 16. By virtue of the relatively slow rotation of the measuring head 12 relative to the base 14, the whole space is scanned step by step, by means of the circles. The entity of measuring points X of such a measurement is designated scan. For such a scan, the center C₁₀ of the laser scanner 10 defines the stationary reference system of the laser scanner 10, in which the base 14 rests. Further details of the laser scanner 10 and particularly of the design of measuring head 12 are described for example in U.S. Pat. No. 7,430,068 and DE 20 2006 005 643, the respective disclosures being incorporated by reference.

To determine the distance d of the measuring points X by means of evaluation of the phase shift, it is sufficient to use only one of the three wave lengths, i.e. the modulated of the three laser beams R, G and B. If necessary, this beam can have a somewhat higher intensity (i.e. power of the electro-magnetic wave) compared to the two other beams. Basically, all wavelengths are suitable to the same extent. With regard to eye protection, which can better be obtained with wavelengths below 400 nm, due to the behavior of the receptors of the human eye, it is, however, advantageous to use the blue laser beam B (with a wavelength shorter than 400 nm), for determining the distances d of the measuring points X. If the two other laser beams R and G are modulated as well, their evaluation can be used for eliminating ambient light or for gaining additional distance information.

In addition to the distance d to the center C₁₀ of the laser scanner 10, each measuring point X comprises color and brightness information which is determined by the control and evaluation unit 22 as well, i.e. the brightness values for any of the three colors of the laser beams R, G and B. Each brightness value corresponds to a gray-tone value which is determined, for example, by integration of the bandpass-filtered and amplified signal of the light receiver 21 over a measuring period which is attributed to the measuring point X, namely for any of the three laser beams R, G, and B separately. All three laser beams R, G and B consequently contribute to gaining the color and brightness information.

Optionally, the light emitter 17 can be designed in such a way that the three laser beams R, G and B can be switched on and off independently of each other and that their intensity can also be controlled. The composition of the emission light beam 18 can then be adapted to the application. If, for example, only the distance d and the brightness (gray-tone value) shall be measured, it is sufficient to use, for example, the blue laser beam B and to let the other two laser beams R and G switched off. A modular design is also possible for the light emitter 17, so that the laser diodes for generating the three laser beams R, G and B can be mounted and dismounted independently of each other, for example, being plug-in components or the like. If applicable, only the laser diode necessary for generating the laser beam which serves to determine the distance d, is mounted permanently. 

The invention claimed is:
 1. A device for optically scanning and measuring an environment, comprising: a laser scanner having a light emitter that emits an emission light beam, having a collimator that collimates the emission light beam, having a light receiver that receives a reception light beam which is reflected by an object in the surroundings of the laser scanner or scattered otherwise, and having a mirror with a reflective surface that both deflects the emission light beam into the environment and deflects the reception light beam onto the light receiver; wherein the laser scanner has a control and evaluation unit that determines a distance to, and color and brightness information of, the object for a multitude of measuring points, and wherein the emission light beam is a superposition of three laser beams having different wavelengths which define a three-dimensional color space, wherein, among the three laser beams, one of the laser beams has a higher intensity than the two other laser beams and is modulated; wherein the laser scanner further has a measuring head that rotates around a vertical axis, and wherein the mirror rotates around a horizontal axis, wherein an intersection point of the vertical axis of rotation and the horizontal axis of rotation defines a stationary reference frame of the laser scanner proximate to which both the emission light beam is deflected into the environment and the reception light beam is deflected onto the light receiver; wherein all three laser beams together serve for determining the color and brightness information for the measuring points; and wherein only the one laser beam having the higher intensity and being modulated is sufficient by itself for determining the distance to the object by determination and evaluation of a phase shift between the emission light beam and the reception light beam of the one laser beam having the higher intensity and being modulated.
 2. The device of claim 1, wherein the light emitter has three laser diodes or other lasers which generate one of the three laser beams each.
 3. The device of claim 2, wherein the superposition of the three laser beams takes place by feeding the three laser beams into a collimator of the light emitter or by feeding them into a common optic fiber, which is then fed to the collimator of the light emitter.
 4. The device of claim 1, wherein, among the three laser beams, the laser beam which serves to determine the distance, has a wavelength which is shorter than 400 nm.
 5. The device of claim 1, wherein the light emitter is configured such that the three laser beams can be switched on and off independently of each other and their intensity can be controlled.
 6. The device of claim 1, wherein the light emitter is configured such that the laser diodes or other lasers for generating the three laser beams can be mounted and dismounted independently of each other.
 7. The device of claim 1, wherein the two other laser beams are modulated and used for eliminating ambient light, for gaining additional distance information, or for error corrections. 